Science + Tech

The value of bleaching

I never thought of bleaching my teeth until my dental school friend raved about using whitening strips. Comparing my teeth to my friend’s, I clearly saw my coffee-colored teeth from 20 years of drinking coffee every day. I bought the whitening strips and slapped them on for 30 minutes.

While I had significant sensitivity the next day (cold beverages and breathing in too fast through my mouth hurt my teeth), I saw my teeth brighten over a few uses. The problem was that only the front of my teeth whitened. The sides of my teeth, the interproximal areas, remained yellow because the strips didn’t adapt well to my teeth. Now it was more apparent how yellow my teeth used to be. I also had restorations on my front teeth from a gymnastic accident that now had visible orange margins.
Whitening strips may work if your teeth are already fairly white, but they produced more problems than solutions for me.

I then made bleaching trays. I bought a 10% carbamide peroxide bleaching solution online, placed no more than 0.5 milliliters of gel in each tray and wore the trays for only an hour versus overnight. I had no sensitivity, and the interproximal and restoration margins cleaned up nicely after seven or so uses. My teeth looked more transparent than Hollywood-smile white. This is a possible outcome of bleaching because stain-free enamel is naturally more like transparent glass than a frosty white. Continued use may have made my teeth whiter, but I don’t think that looks as natural. I stopped using the trays once the yellow borders disappeared.

Helping patients select the best bleaching method
Many people take on bleaching treatment themselves. They can order bleaching materials online or have their teeth bleached at a salon or at the mall. However, bleaching is not for everyone. The results vary based on the method used. That’s why it’s best for people to consult dentists since they are knowledgeable about bleaching and how to do it safely.

As a dental student, you can help patients determine what bleaching method will be best for them based on the types of stains they have and which of their teeth are vital.

First it’s important to understand a tooth’s color is influenced by intrinsic factors like the color of the dentin and extrinsic factors like stains on the enamel surface. A prophylactic cleaning by a hygenist or an abrasive whitening toothpaste may remove surface-level stains, but deeper stains may require bleaching.

Second, know that there are two broad categories of products that can whiten teeth: 1) those that abrade the tooth surface and 2) those that chemically treat teeth with bleaching agents.

Stains on the teeth’s outer surface can be removed with whitening toothpaste containing abrasive compounds like pyrophosphates or pumice or by a hygienist using pumice pastes during a professional cleaning. Teas, coffee, wine, curry, brightly colored fruits, beets and tomato sauces often cause these stains, according to a March 2016 article by Tufts University. If a patient chooses to use whitening toothpaste, advise them not to brush too hard or use a toothpaste that is too abrasive to avoid damaging healthy, protective enamel or causing sensitivity. Any toothpaste with the ADA seal of approval has a safe abrasiveness level for regular use. Still, encourage patients to review this list of abrasive toothpaste before choosing one.

In contrast, intrinsic stains are usually addressed chemically by oxidizing organic pigments in the teeth. Intrinsic stains can come in many forms. Yellowing can come from the natural color of dentin or chromogenic foods. Gray coloring can come from dentin bruising due to tooth trauma or tetracycline or minocycline use. In either case, the extent of the staining will impact bleaching time. Most products addressing intrinsic stains contain hydrogen peroxide, which oxidizes within 30 minutes of application.

Hydrogen peroxide is usually the active ingredient in stick-on whitening strips and whitening “pens,” which is why they’re typically used at a higher concentration for a shorter period. Some toothpastes also contain small amounts of hydrogen peroxide, but since they don’t remain for long on teeth, their effects are less significant.

If you make bleaching trays, the trays will need a bleaching gel. These gels are usually thick so they stick to teeth. Carbamide peroxide, also known as urea hydrogen peroxide, is the typical active ingredient. It breaks down into water, urea and oxygen and then decomposes into ammonia and CO2 gas (the CO2 gas causes bubbles to form in the gel as you wear it, a built-in way to confirm the product is working).

Carbamide peroxide breaks down more slowly. It’s typically worn overnight in trays to gain the full effect. Patients should use bleaching trays for up to two weeks and re-evaluate if it’s necessary to continue. The average treatment time is five to six weeks.

Patients should spit out excess bleaching solution before long-term wear, but swallowing small amounts of a low-concentration formula poses no risk. Significant side effects of using bleaching trays are mild gingival irritation and tooth sensitivity that resolve in one to three days.

Keep in mind the only way to change the color of fillings and crowns is to replace them. Track your patient’s bleaching over time to pick a color that matches their existing restoration colors.

If a patient is concerned about discoloration of a root canal-treated tooth, a walking bleach technique may be used, placing sodium perborate directly into the canal of the tooth. The patient will likely need to consult an endodontist on this type of procedure. Tell your patients to abstain from bleaching for at least two weeks before any planned restoration procedures as bleaching decreases the effectiveness of bonding materials used in restorative dentistry and increases the risk of restoration failure.

We’ve only scratched the surface on what to consider when deciding the best bleaching method for your patients. While the available bleaching options may seem overwhelming, most rely on the same basic ingredients to produce results. You should carefully assess each patient and provide a comprehensive treatment plan before making bleaching trays. Reassure your patients that while they can receive bleaching treatments elsewhere, it’s best to consult a dentist to create a bleaching treatment plan because they are highly knowledgeable, held to high professional standards and have the best interests of the patient at heart.

~ Margaret McGuire, North Carolina ‘24

Margaret McGuire

Margaret McGuire, North Carolina - Chapel Hill ’24, is co-president of the UNC chapter’s Student Professionalism and Ethics Association, enjoys research and runs the UNC Student Research Group Journal Club. In her free time, she makes art, runs, plays in a band with dental school friends and sleeps eight hours every night (usually).

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1 Comment

  1. Hello Margaret,
    Thanks for this post. I really liked it and got to know many new things. Keep it up.

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